Prior art seaming elements (e.g. WO 2010/121360 (Manninen)) can include nonwoven seaming elements which are formed from an oriented polymer film. One of a pair of such seaming elements can be attached at each end or edge of a textile to be joined, and looped portions at the free edge regions of the two elements can be interdigitated to provide a channel suitable for receiving a securing means such as a pintle. The dimensions for the seaming elements are selected so as to be compatible with the textile to be seamed, in particular as to thickness so as to minimize or avoid any discontinuity at the seaming area.
For the manufacture of such seaming elements, it is also known to use conventional methods of roll-forming, such as that disclosed in WO 2014/075170 (Manninen).
It is also known from WO 2011/100157 (Breuer et al.) to provide a double set of loops constructed from warp yarns in the seaming area of a woven fabric, through each of which sets a pintle can be inserted. However, the double set of loops are connected to and integral with the body of the entire fabric, and there is no suggestion of providing a distinct and separate seaming element unit for later attachment to a variety of types of industrial textile, woven or non-woven, single layered or multilayered.
It is also known from WO 2013/086609 (Manninen) that such a separate seaming element can be constructed so as to provide two or more looped regions, thereby creating at least two channels across the seam, which allows for improved distribution of the tensile load across the element.
Such channels can be dimensioned so as to provide sufficient space in which the free ends of pintles can be turned back into the channel to secure the ends. These seaming elements can be secured to the seamable end or edge of the textile by any suitable means, including bonding, either to compressed yarn ends of a woven textile, or to appropriate selected surfaces of a non-woven textile, including a textile comprising one or more layers of film. The elements are constructed from two folded layers of film, one secured inside the other, or as a molded structure having the same cross-section as the two layer construction.
In addition, EP 2511567 (B1) (Frey) discloses a method for manufacturing a strip of material in a loop. The method includes the steps of splitting each of ends of a conveyor belt in order to separate an upper face from a lower face of the belt. In each zone, transverse holes are formed. A transverse pin is then arranged in each zone. The upper and lower faces of the belt are then put back together, and the pin is removed.
It has now been found that two channels can be provided in a structure comprising a single folded layer of film.